Direct-current power grid converter station grounding fault ultra-high-speed protection method

Abstract

The invention relates to a direct-current power grid converter station grounding fault ultra-high-speed protection method. A current transformer is arranged on the bridge arm of a converter in a direct-current power grid, and is used for detecting the over-current of the bridge arm and giving out alternating-current grounding fault criterion of the converter; for each converter station, a converter station alternating-current grounding fault and a direct-current line fault are distinguished according to the criterion, and whether an alternating-current grounding fault exists in the converter station or not is judged, and if the alternating-current grounding fault exists, a locking signal is sent to direct-current side protection, so that the operation of a direct current circuit breaker isavoided; meanwhile, the fault converter is locked, and the fault current is limited; a current-limiting inductor and a circuit breaker are installed in a direct-current power grid metal return line,and are used for limiting the fault current of the fault converter and cutting off a discharging loop; the metal return line direct-current circuit breaker closest to the fault converter station receives a signal and then acts, the fault current path is blocked, the alternating-current circuit breaker trips, an alternating-current path is blocked, and then all the non-fault converter stations continuously run normally.

Description

technical field [0001] The invention relates to the fields of relay protection and automation of electric power systems, in particular to an ultra-high-speed protection method for grounding faults of converter stations of MMC DC power grids with symmetrical bipolar wiring structure. Background technique [0002] In recent years, my country's wind power, photovoltaic power generation and other renewable energy installed capacity has continued to expand, making the power generation center far away from the load center. The high-voltage direct current transmission method has gained great attention and development because it is suitable for long-distance and large-capacity power transmission. At present, MMC converters with active and reactive power independent control properties are widely used in flexible direct current transmission projects, and have the advantages of high output voltage level, low switching loss and good output voltage waveform. [0003] Although the use of...

AI Technical Summary

Problems solved by technology

[0004] The invention proposes a method for judging the AC grounding fault of the converter station based on the current differential of the bridge arm of the converter. The method only uses the current of the bridge arm of the converter, and can accurately detect the faulty converter station. Based on the method, a set of protection schemes for converter stations suitable for DC power grids are designed to solve the protection problems of AC ground faults in converter stations in DC power grids.

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